This invention relates to two cycle engine provided with a scavenging pump and more particularly to an improved scavenging system for a two cycle engine.
It has been the practice to provide multiple scavenging ports for a two cycle engine in order to achieve better scavenging and to control the flow pattern within the combustion chamber and cylinder during the scavenging operation. For example, it is quite common to use a center and a pair of side scavenging ports that have an upward inclination so as to direct a charge entering the chamber in an upward direction toward the cylinder head to establish a loop type of scavenging action in the combustion chamber. It should be readily apparent that it is desirable to provide good scavenging of the exhaust gases and, at the same time, avoid the escape of any fresh air and fuel charge from the combustion chamber out of the exhaust port.
A disadvantage with the type of scavenging systems previously proposed is that a single scavenge manifold encircles or partially encircles the cylinder and each of the scavenge ports are fed from this scavenge manifold through respective riser portions. As a result, there is a different flow resistance from the scavenge air inlet to the various scavenge ports and the scavenge ports most remotely positioned from the inlet may not receive the desired amount of air flow. Alternatively, the more closely positioned scavenge ports may receive a greater than desired air flow.
It is, therefore, a principal object of this invention to provide an improved scavenging system for a two cycle engine wherein a plurality of scavenge ports may each be provided with the desired air flow without the flow to one scavenge port adversely affecting the flow to the other scavenge ports.
It is a further object of this invention to provide an improved scavenge port and manifolding system for a two cycle engine.
It is a further object of this invention to provide a scavenge porting and supply arrangement for a two cycle engine that permits the achievement of the desired scavenging pattern in the combustion chamber.